Recent years have seen growing social needs for a system which, in the event of occurrence of an emergency situation, such as an earthquake or a tsunami, can notify emergency information about the emergency to many people immediately. On the other hand, the market size of mobile terminals, such as mobile phones, is increasing year by year. In Japan, the market size has reached more than 90 million sets of mobile terminals and there occur social circumstances in which many persons own a mobile phone. Therefore, information delivery using mobile terminals via a mobile communications network can be made to serve as an effective notifying means of notifying emergency information.
As a system for notifying emergency information, for example, J-ALERT (a nationwide instantaneous alert system) has been examined. This nationwide instantaneous alert system is assumed to use a municipal disaster prevention radio to notify emergency information by way of speakers for disaster broadcasting which are mainly installed indoors and outdoors. However, this nationwide instantaneous alert system using speakers to notify, by voice, emergency information causes a case in which those who live in an area distant from the speakers and so on cannot know the emergency information.
To solve this problem, there has been proposed a system that notifies, by voice or by using an e-mail, emergency information to mobile terminals, which users who are registered to receive a service manage respectively, via an existing mobile communications network. Furthermore, there has been also considered a method of broadcasting emergency information to an indefinite number of users by using digital terrestrial broadcasting.
As a service for broadcasting information to an indefinite number of users in a mobile communications system, there has been provided, for example, a CBS (Cell Broadcast Short message service) (refer to nonpatent reference 1). This CBS is a point-to-multipoint (Point to Multipoint) service which enables abase station which provides a service in a mobile communications system to carry out broadcast communications with mobile terminals which are registered into the base station and have come under the control of the base station. It is defined according to the 3GPP (3 rd Generation Partnership Project) that each mobile terminal can be placed in either one of the following states: an Idle state, a CELL_DCH state, a CELL_FACH state, a CELL_PCH state, and a URA_PCH state (refer to nonpatent reference 2). In the mobile communications system, each mobile terminal operates while making a transition among these states whenever necessary.
Furthermore, as a conventional emergency information notifying system using a mobile communications network, for example, patent reference 1 discloses an emergency information notifying system. This emergency information notifying system uses broadcast information which a base station transmits to all the mobile terminals being under the control thereof for notification of emergency information. The emergency information notifying system adds, as parameters, channel information used for reception of the emergency information and an identifier of the emergency information to this broadcast information, so that all the mobile terminals can receive a channel via which the emergency information is transmitted thereto on the basis of these parameters.
On the other hand, as a service suitable for transmitting emergency information to an indefinite number of user terminals in a mobile communications system, a broadcast type multimedia service which enables simultaneous delivery of one transmission data to a plurality of users' mobile terminals has been studied. In this broadcast type multimedia service, especially, multimedia information about sports live broadcasting, a weather forecast, a radio, or the like is delivered simultaneously to a plurality of users' mobile terminals as a service of the mobile communications system. In the 3GPP, this technology is called an MBMS (Multimedia Broadcast Multicast Service) (refer to nonpatent reference 3).
In the MBMS, it is assumed that a multimedia service as mentioned above is provided, and a fast transfer of a moving image or the like is supported. Therefore, as compared with the CBS, a larger amount of information can be transmitted at a higher rate, and the MBMS is suitable for a system for broadcasting emergency information according to the needs of an indefinite number of users.
As channels in a wireless section used for the MBMS, as shown in nonpatent reference 3, three logical channels (an MCCH, an MTCH, and an MSCH) are introduced, and an MICH (MBMS Indicator CHannel) is introduced as an indicator similar to a PICH. The MCCH (MBMS Control CHannel) is a channel on which control information about the MBMS is carried, and the MTCH (MBMS Traffic CHannel) is a channel on which data about the MBMS are carried. The MICH has the same physical structure as the PICH based on the R99 (release 99) standard in the 3GPP, and, when information is carried on the MCCH, this bit is set in advance.
A mobile terminal receives data about the MBMS which are carried on the MTCH according to the MBMS control channel (MCCH). When certain information is carried on the MCCH, the bit of the MICH which is an indicator for MBMS notification is set, and, after recognizing the bit, the mobile terminal receives the MCCH on which new control information is carried. In this case, the mobile terminal receives the MTCH on which data about the MBMS are carried according to the newly received MCCH.
Furthermore, the procedure for receiving the MCCH does not depend on the state in which the mobile terminal can enter (the Idle state, and the RRC connected state (RRC_Connected) (the CELL_DCH state, the CELL_FACH state, the CELL_PCH state, or the URA_PCH state)), and can be applied to all mobile terminals which support the MBMS (refer to nonpatent reference 4). Therefore, even if a mobile terminal is placed in any of the above-mentioned states, the mobile terminal can receive data about the MBMS.
According to the 3GPP, as a communications method different from W-CDMA, a new communications method which is called “long term evolution” (Long Term Evolution LTE) for a wireless section and which is also called “system architecture evolution” (System Architecture Evolution SAE) for a whole system structure including a core network has been examined. In an access method for LTE, OFDM (Orthogonal Frequency Division Multiplexing) is used for a downlink direction, while SC-FDMA (Single Career Frequency Division Multiple Access) is used for an uplink direction. The bandwidth in the case of W-CDMA is 5 MHz, while the bandwidth in the case of LTE can be selected from among 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz for each and every base station. Furthermore, in the case of LTE, no circuit switching is included, unlike in the case of W-CDMA, only a packet communications method is included.
In an LTE communications system, a base station (Base station) that communicates with a mobile terminal (UE: User Equipment) is called an eNB (E-UTRANNodeB), and a base station control apparatus (Radio Network Controller) which performs exchange of control data and user data with a plurality of base stations is called an EPC (Evolved Packet Core) (also called an aGW: Access Gateway). In this LTE communications system, a unicast (Unicast) service and an E-MBMS service (Evolved Multimedia Broadcast Multicast Service) are provided. The E-MBMS service is a broadcast type multimedia service, and may be simply called an MBMS. A large-amount broadcast content, such as a news content, a weather forecast content, or a mobile broadcasting content, is transmitted to a plurality of mobile terminals. This is also called a point-to-multipoint (Point to Multipoint) service.
The current determined matters of the whole architecture (Architecture) of LTE systems in the 3GPP are described in nonpatent reference 5. The whole architecture will be explained with reference to FIG. 11 (refer to Chapter 4 of nonpatent reference 5). FIG. 11 is an explanatory drawing showing the structure of a communications system according to an LTE method. In FIG. 11, if a control protocol (e.g. RRC (Radio Resource Management)) and a user plane (e.g. PDCP: Packet Data Convergence Protocol, RLC: Radio Link Control, MAC: Medium Access Control, PHY: Physical layer) for a mobile terminal 101 are terminated at a base station 102, an E-UTRAN (Evolved Universal Terrestrial Radio Access) is constructed of one or more base stations 102. Each base station 102 carries out scheduling (Scheduling) and transmission of a paging signal (Paging Signaling, which is also called a paging message (paging message)) which is notified from an MME (Mobility Management Entity) 103. The base stations 102 are connected to one another via an X2 interface. Furthermore, each base station 102 is connected to an EPC (Evolved Packet Core) via an S1 interface. More specifically, each base station 102 is connected to an MME (Mobility Management Entity) 103 via an S1_MME interface, and is connected to an S-GW (Serving Gateway) 104 via an S1_U interface. Each MME 103 distributes a paging signal to a plurality of base stations 102 or a single base station 102. Furthermore, each MME 103 performs mobility control (Mobility control) in an idle state (Idle State). Each S-GW 104 performs transmission and reception of user data to and from one or more base stations 102.
The current determined matters about the frame structure of LTE systems in the 3GPP are described in nonpatent reference 5 (Chapter 5). They will be explained with reference to FIG. 12. FIG. 12 is an explanatory drawing showing the structure of a radio frame for use in a communications system using an LTE method. In FIG. 12, one radio frame (Radio frame) has a length of 10 ms. The radio frame is divided into ten equal-sized sub-frames (Sub-frames). Each of the sub-frames is divided into two equal-sized slots (slots). A downlink synchronous channel (Downlink Synchronization Channel: SCH) is included in each of the first (#0) and sixth (#5) sub-frames of every frame. Synchronizing signals include a primary synchronization channel (Primary Synchronization Channel: P-SCH) and a secondary synchronization channel (Secondary Synchronization Channel: S-SCH). Multiplexing of channels for MBSFN (Multimedia Broadcast multicast service Single Frequency Network) and channels other than the channels for MBSFN is performed on a sub-frame basis. Hereafter, sub-frames for MBSFN transmission are called MBSFN sub-frames (MBSFN sub-frames). In nonpatent reference 5, an example of signaling at the time of assignment of MBSFN sub-frames is described. FIG. 13 is an explanatory drawing showing the structure of MBSFN frames. As shown in FIG. 13, MBSFN sub-frames are assigned to every MBSFN frame (MBSFN frame). MBSFN frame clusters (MBSFN frame Clusters) are scheduled. The repetition period (Repetition Period) of the MBSFN frame clusters is assigned.
The current determined matters about the channel configuration of LTE systems in the 3GPP are described in nonpatent reference 5. Physical channels (Physical channels) will be explained with reference to FIG. 14 (refer to Chapter 5 of nonpatent reference 5). FIG. 14 is an explanatory drawing explaining physical channels for use in a communications system according to an LTE method. In FIG. 14, a physical broadcast channel 401 (Physical Broadcast channel: PBCH) is a downlink channel which is transmitted from a base station 102 to a mobile terminal 101. BCH transport blocks (transport blocks) are mapped to four sub-frames during an interval of 40 ms. There is no clear signaling at a timing of 40 ms. A physical control channel format indicator channel 402 (Physical Control format indicator channel: PCFICH) is transmitted from the base station 102 to the mobile terminal 101. The PCFICH is used to notify the number of OFDM symbols which are used for PDCCHs from the base station 102 to the mobile terminal 101. The PCFICH is transmitted for every sub-frame. A physical downlink control channel 403 (Physical downlink control channel: PDCCH) is a downlink channel which is transmitted from the base station 102 to the mobile terminal 101. The PDCCH is used to notify resource allocation (allocation), HARQ information about a DL-SCH (a downlink shared channel which is one of transport channels shown in FIG. 15), and a PCH (a paging channel which is one of the transport channels shown in FIG. 15). The PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant). The PDCCH carries ACK/Nack which is a response signal to uplink transmission. A physical downlink shared channel 404 (Physical downlink shared channel: PDSCH) is a downlink channel which is transmitted from the base station 102 to the mobile terminal 101. A DL-SCH (a downlink shared channel) which is a transport channel is mapped to the PDSCH. A physical multicast channel 405 (Physical multicast channel: PMCH) is a downlink channel which is transmitted from the base station 102 to the mobile terminal 101. An MCH (multicast channel) which is a transport channel is mapped to the PMCH.
A physical uplink control channel 406 (Physical Uplink control channel: PUCCH) is an uplink channel which is transmitted from the mobile terminal 101 to the base station 102. The PUCCH carries ACK/Nack which is a response signal (response) to downlink transmission. The PUCCH carries a CQI (Channel Quality indicator) report. CQI is quality information showing either the quality of received data or channel quality. A physical uplink shared channel 407 (Physical Uplink shared channel: PUSCH) is an uplink channel which is transmitted to the base station 102 from the mobile terminal 101. A UL-SCH (uplink shared channel which is one of the transport channels shown in FIG. 15) is mapped to the PUSCH. A physical HARQ indicator channel 408 (Physical Hybrid ARQ indicator channel: PHICH) is a downlink channel which is transmitted from the base station 102 to the mobile terminal 101. The PHICH carries ACK/Nack which is a response to uplink transmission. A physical random access channel 409 (Physical random access channel: PRACH) is an uplink channel which is transmitted from the mobile terminal 101 to the base station 102. The PRACH carries a random access preamble (random access preamble).
The transport channels (Transport channels) will be explained with reference to FIG. 15 (refer to Chapter 5 of nonpatent reference 5). FIG. 15 is an explanatory drawing explaining the transport channels for use in a communications system according to an LTE method. Mapping between the downlink transport channels and the downlink physical channels is shown in FIG. 15A. Mapping between the uplink transport channels and the uplink physical channels is shown in FIG. 15B. As to the downlink transport channels, a broadcast channel (Broadcast channel: BCH) is broadcast to all the base stations (cell). The BCH is mapped to the physical broadcast channel (PBCH). Retransmission control with HARQ (Hybrid ARQ) is applied to the downlink shared channel (Downlink Shared channel: DL-SCH). A broadcast to all the base stations (cell) can be carried out. Dynamic or semi-static (Semi-static) resource allocation is supported. Semi-static resource allocation is also referred to as persistent scheduling (Persistent Scheduling). In order to decrease the power consumption of a mobile terminal, DRX (Discontinuous reception) of the mobile terminal is supported. The DL-SCH is mapped to the physical downlink shared channel (PDSCH). The paging channel (Paging channel: PCH) supports the DRX of the mobile terminal in order to enable decrease in the power consumption of the mobile terminal. A request for a broadcast to all the base stations (cell) is made. It is mapped to either a physical resource like the physical downlink shared channel (PDSCH) which can be dynamically used for traffic, or a physical resource like the physical downlink control channel (PDCCH) which is another control channel. The multicast channel (Multicast channel: MCH) is used for a broadcast to all the base stations (cell). SFN combining of MBMS services (the MTCH and the MCCH) in multi-cell transmission is supported. Semi-static resource allocation is supported. The MCH is mapped to the PMCH.
Retransmission control with HARQ (Hybrid ARQ) is applied to the uplink shared channel (Uplink Shared channel: UL-SCH). Dynamic or semi-static (Semi-static) resource allocation is supported. The UL-SCH is mapped to the physical uplink shared channel (PUSCH). A random access channel (Random access channel: RACH) shown in FIG. 15B is limited to control information. There is a risk of collision. The RACH is mapped to the physical random access channel (PRACH).
The logical channels (Logical channels) will be explained with reference to FIG. 16 (refer to Chapter 6 of nonpatent reference 5). FIG. 16 is an explanatory drawing explaining the logical channels for use in a communications system according to an LTE method. Mapping between the downlink logical channels and the downlink transport channels is shown in FIG. 16A. Mapping between the uplink logical channels and the uplink transport channels is shown in FIG. 16B. A broadcast control channel (Broadcast control channel: BCCH) is a downlink channel for broadcast system control information. The BCCH which is a logical channel is mapped to either the broadcast channel (BCH) which is a transport channel or the downlink shared channel (DL-SCH). A paging control channel (Paging control channel: PCCH) is a downlink channel for transmitting a paging signal. The PCCH is used when the network does not know the cell location of a mobile terminal. The PCCH which is a logical channel is mapped to the paging channel (PCH) which is a transport channel. A common control channel (Common control channel: CCCH) is a channel for transmission of control information between a mobile terminal and a base station. The CCCH is used when the mobile terminal does not have any RRC connection (connection) with the network. Whether to dispose the CCCH in the downlink is not decided at the current time. In the uplink direction, the CCCH is mapped to the uplink shared channel (UL-SCH) which is a transport channel.
The multicast control channel (Multicast control channel: MCCH) is a downlink channel for point-to-multipoint transmission. This channel is used for transmission of one or more pieces of MEMS control information for MTCH from the network to a mobile terminal. The MCCH is used only for a mobile terminal which is receiving an MBMS. The MCCH is mapped to either the downlink shared channel (DL-SCH) which is a transport channel or the multicast channel (MCH). A dedicated control channel (Dedicated control channel: DCCH) is a channel used for transmission of individual control information between a mobile terminal and the network. The DCCH is mapped to the uplink shared channel (UL-SCH) in the uplink, while the DCCH is mapped to the downlink shared channel (DL-SCH) in the downlink. A dedicated traffic channel (Dedicate Traffic channel: DTCH) is a channel used for point to point communications with an individual mobile terminal for transmission of user information. The DTCH exists for both the uplink and the downlink. The DTCH is mapped to the uplink shared channel (UL-SCH) in the uplink, while the DTCH is mapped to the downlink shared channel (DL-SCH) in the downlink. The multicast traffic channel (Multicast Traffic channel: MTCH) is a downlink channel used for transmission of traffic data from the network to a mobile terminal. The MTCH is used only for a mobile terminal which is receiving an MBMS. The MTCH is mapped to either the downlink shared channel (DL-SCH) or the multicast channel (MCH).
The current determined matters about an E-MBMS service in the 3GPP are described in nonpatent reference 5. The definition of terms about E-MBMS will be explained with reference to FIG. 17 (refer to Chapter 15 of nonpatent reference 5). FIG. 17 is an explanatory drawing explaining a relation between an MBSFN synchronization area and an MBSFN area. In FIG. 17, the MBSFN synchronization area 701 (Multimedia Broadcast multicast service Single Frequency Network Synchronization Area) is an area of the network in which all the base stations can be synchronized with one another and can carry out MBSFN (Multimedia Broadcast Multicast service Single Frequency Network) transmission. The MBSFN synchronization area includes one or more MBSFN areas (MBSFN Areas) 702. In one frequency layer (frequency layer), each base station has no alternative but to belong to only one MBSFN synchronization area. Each MBSFN area 702 (MBSFN Area) consists of a group of base stations (cell) included in the MBSFN synchronization area of the network. Base stations (cell) included in the MBSFN synchronization area may construct a plurality of MBSFN areas.
The logical architecture (Logical Architecture) of the E-MBMS will be explained with reference to FIG. 18 (refer to Chapter 15 of nonpatent reference 5). FIG. 18 is an explanatory drawing explaining the logical architecture (Logical Architecture) of the E-MBMS. In FIG. 18, a multi-cell/multicast coordination entity 801 (Multi-cell/multicast Coordination Entity: MCE) is a logical entity. The MCE 801 allocates radio resources to all the base stations in the MBSFN area in order to carry out multi-cell MBMS transmission (multi-cell MBMS transmission). The MCE 801 makes a decision about the details of the radio structure (e.g. a modulation method and codes) in addition to allocation of time or/and frequency radio resources. An E-MEMS gateway 802 (MBMS GW) is a logical entity. The E-MBMS gateway 802 is located between an eBMSC and base stations, and has amain function of transmitting/broadcasting an MEMS service to each of the base stations according to the SYNC protocol. An M3 interface is a control interface (Control Plane Interface) between the MCE 801 and the E-MBMS gateway 802. An M2 interface is a control interface between the MCE 801 and an eNB 102. An M1 interface is a user data interface (User Plane Interface) between the E-MBMS gateway 802 and the eNB 102.
The architecture (Architecture) of the E-MBMS will be explained (refer to Chapter 15 of nonpatent reference 5). FIG. 19 is an explanatory drawing explaining the architecture (Architecture) of the E-MBMS. As shown in FIGS. 19A and 19B, there can be considered two cases of the architecture of the E-MBMS. A cell for the MBMS will be explained (refer to Chapter 15 of nonpatent reference 5). In an LTE system, there are an MEMS-dedicated cell (base stations) (an MBMS-dedicated cell), and an MBMS/Unicast-mixed cell (MBMS/Unicast-mixed cell) which can perform both an MBMS and a unicast service.
MBMS transmission will be explained (refer to Chapter 15 of nonpatent reference 5). In the MBMS transmission in an LTE system, single-cell transmission (Single-cell transmission: SC transmission) and multi-cell transmission (multi-cell transmission: MC transmission) are supported. In the single-cell transmission, any SFN (Single frequency Network) operation is not supported. In contrast, in the multi-cell transmission, an SFN operation is supported. In the MBSFN (Multimedia Broadcast multicast service Single Frequency Network) area, transmission of an MBMS is synchronized. SFN combining (Combining) of MBMS services (the MTCH and the MCCH) in the multi-cell transmission is supported. The MTCH and the MCCH are mapped to the MCH in point-to-multipoint transmission. Scheduling is performed by the MCE.
The structure (Structure) of the Multicast control channel (MCCH) will be explained (refer to Chapter 15 of nonpatent reference 5). The broadcast control channel (BCCH) which is a downlink logical channel shows scheduling of one or two primary multicast control channels (Primary MCCHs: P-MCCHs). A P-MCCH for single-cell transmission is mapped to the DL-SCH (downlink shared channel). Furthermore, a P-MCCH for multi-cell transmission is mapped to the MCH (multicast channel). When a secondary multicast control channel (Secondary MCCH: S-MCCH) is mapped onto the MCH, the address of the secondary multicast control channel (S-MCCH) can be shown by using the primary multicast control channel (P-MCCH). The broadcast control channel (BCCH) shows the resource of the primary multicast control channel (P-MCCH), but does not show any available service.
The current determined matters about paging in the 3GPP are described in nonpatent reference 5 (Chapter 10). A paging group uses an L1/L2 signaling channel (PDCCH). The precise identifier (UE-ID) of a mobile terminal can be identified on the paging channel (PCH).    [Nonpatent reference 1] 3GPP technical specifications TS23.041 V3.5.0    [Nonpatent reference 2] W-CDMA mobile communications system, compiled under the supervision of Keiji Tachikawa and published on Jun. 6, 2001, pages 162-171    [Nonpatent reference 3] 3GPP technical specifications TS25.346 V7.3.0    [Nonpatent reference 4] 3GPP technical specifications TS25.331 V6.6.0    [Nonpatent reference 5] 3GPP technical specifications TS36.300 V8.2.0    [Patent reference 1] Japanese Patent Gazette No. 3529351
Because conventional mobile communications systems are constructed as mentioned above, a problem with them is that they are easily affected by the influence of the load on the communications line when they are used as a system for broadcasting emergency information to an indefinite number of users, the area in which emergency information can be delivered is narrow, and the immediacy of the information may be impaired.
To be more specific, a conventional system that notifies emergency information, via an existing mobile communications network, to users' mobile terminals by voice or by using an e-mail carries out provision of information via one-to-one communications between each of mobile terminals owned by users who are registered to receive the service and a base station which provides this service. Therefore, because the service depends upon the capacity of the communications line between the base station and the mobile terminals, there occurs a case in which the load on the communications line increases and therefore the conventional system cannot notify emergency information to the mobile terminals when the number of users to whom the conventional system notifies the emergency information increases. Therefore, the conventional system is not suitable for notification of emergency information to an indefinite number of users.
Furthermore, in a conventional system that notifies emergency information by using digital terrestrial broadcasting, as compared with a system using a mobile communications network, there are many locations where the receiving characteristics of digital terrestrial broadcasting waves degrade, such as an indoor, the shade of a building, and an underground shopping area, and there may be a case in which emergency information cannot be broadcast precisely. In addition, because it is necessary to add hardware used for receiving digital terrestrial broadcasting to each mobile terminal, the conventional system has a demerit for the downsizing and low pricing of mobile terminals.
A base station carries out point-to-multipoint communications with mobile terminals in the case of the CBS, and therefore the CBS is suitable for notification of emergency information to an indefinite number of users. However, when a base station broadcasts data to mobile terminals, all of the mobile terminals cannot receive the transmission data and only mobile terminals in an idle (Idle) state can receive the transmission data. As mentioned above, each of the mobile terminals is operating while making a transition among a plurality of states defined by the 3GPP on an as needed basis. Therefore, although each mobile terminal can receive the emergency information broadcast thereto when it is placed in the idle (Idle) state, each mobile terminal cannot receive the emergency information broadcast thereto when it is placed in a state other than the idle (Idle) state, and therefore there is a case in which the emergency information is not notified precisely to each mobile terminal.
Furthermore, the CBS is predicated on transmission of a short message at a lower rate of about 80 octets from a base station. Therefore, the short message defined for the CBS does not have a data amount enough to notify emergency information, such as map information or picture information, according to the needs of users.
In contrast with this, the system disclosed by patent reference 1 can broadcast emergency information to all the mobile terminals being registered into a base station and being under the control of the base station. However, what type of channel is used as the channel via which emergency information is transmitted is not specified in patent reference 1. Therefore, whether a dedicated channel, a broadcast channel, or a special channel is used as the channel via which emergency information is transmitted is unknown, and at what rate the emergency information can be transmitted and whether the emergency information meets the needs of users are not known at all.
In addition, in the system disclosed by patent reference 1, because channel information for receiving the emergency information and the identifier of the emergency information have to be added to broadcast information as parameters, the amount of information which should be transmitted as the broadcast information increases unavoidably. In general, many pieces of system information required for a base station to transmit broadcast information to all the mobile terminals being under the control thereof have to be included in the broadcast information. Therefore, it is also expected that the use of the method of adding the parameters for transmitting emergency information to broadcast information causes a necessity to limit the data amount of the parameters for transmitting emergency information in consideration of the amount of information to be transmitted as the broadcast information, and an excessive increase in the amount of information of the broadcast information to which the parameters are added.
In contrast, in the case of the MBMS, because each mobile terminal can receive information even if it is placed in which state defined in the 3GPP, and can receive a fast transfer of data, such as a moving image, emergency information data having an amount of information which meets the needs of users can be transmitted to each mobile terminal. Furthermore, because it is not necessary to include any additional information in broadcast information, unlike in the case of the system disclosed by patent reference 1, the malfunctions which can be expected to occur in the system disclosed by above-mentioned patent reference 1 can be eliminated.
A problem with a conventional mobile communications system which performs an MBMS is, however, that the conventional mobile communications system can deliver multimedia information to a plurality of users' mobile terminals simultaneously, while each user side cannot receive provision of any information unless it initiatively receives an MTCH on which desired data are carried, and therefore the immediacy of emergency information may be impaired.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a mobile communications system that can notify emergency information by using a broadcast type multimedia service being able to provide the emergency information for a wide area without imposing an excessive load on a mobile communications network and without impairing the immediacy of the emergency information, and a base station and a mobile terminal which construct this mobile communications system.